Subhendu Maity

Development of an Automated Regional Coupled Atmosphere-Ocean Modeling System for Coastal Kalpakkam

In this paper the development of an automated flux coupling mechanism applied to a Regional Coupled Atmosphere-Ocean Model (RCAOM) is reported. The coupler serves as an interface between two state-of-the-art models viz. Advanced Weather Research and Forecasting Model (WRF) and Princeton Ocean Model (POM). It has direct significance for ocean state forecasting studies such as prediction of sea-surface temperature (SST), surface circulations etc. RCAOM simulates local processes like upwelling along coastal Kalpakkam situated on the east coast of India and is also used to observe thermal recirculation at intake locations of cooling Jetties for the two nuclear power plants, Madras Atomic Power Plant (MAPS) and Prototype Fast Breeder Reactor (PFBR). The simulations reveal that the rise of temperature at intake locations of MAPS and PFBR occurs due to reversal wind system and exchange of heat fluxes and secondly upwelling is observed at the outfall location due to topographically induced effect in the absence of thermal discharge.

Effect of Atmospheric Forcing on Plume Dispersion and Study of Nuclear Effluent Trajectories for the Kalpakkam Coast, India

AbstractThe air–sea interaction process and its implication at the outfall location of a nuclear power plant have been studied using the Princeton ocean model (POM) under varied environmental forcing parameters (momentum and heat fluxes). In the first set of numerical experiments, constant momentum flux is used with reversing wind speeds of 2 and 10  ms−1 respectively. It is observed that with an increase in wind speed, the plume exhibited a narrow directional spread unlike that for low winds. Incorporation of constant heat flux and momentum flux showed marginal difference in the computed sea surface temperature (SST) at the outfall location. In the second set of experiments, variable momentum and heat fluxes were introduced that led to significant variations in SST, salinity, and circulation patterns. A net variation of approximately 2–3°C in SST has been recorded at the outfall location. Finally, the POM and the particle-trajectory tracking model (PTTM) have been integrated to trace the nuclear effluent...

Reynolds Stress Anisotropy Based Turbulent Eddy Viscosity Model Applied to Numerical Ocean Models

The present state-of-the-art ocean models use an eddy viscosity that depends on structure parameter (Cμ ). In this paper we use a Reynolds stress anisotropy based formulation for the eddy viscosity because in addition to the value of turbulent kinetic energy, it also depends on the degree of anisotropy. The formulation is incorporated into the General Ocean Turbulence Model (GOTM) and simulated using the famous test case of Ocean Weather Station (OWS) Papa experiment. Even if there is not much of an improvement in terms of results with this model, it can be very easily incorporated into the ocean models removing cumbersome equations for structure parameters.

Modeling of turbulent dissipation and its validation in periodically stratified region in the Liverpool Bay and in the North Sea

The present work explores the applicability of an alternative eddy viscosity formulation in numerical models dealing with the dynamics of the coastal ocean. The formulation is based on the Reynolds stress anisotropy–anisotropy being an important tool for capturing turbulent mixing. Initially idealized entrainment scenarios are evaluated that are typical for shelf seas viz. entrainment in linearly stratified and two-layer fluids caused by surface wind stress or barotropic pressure gradient-driven bottom stress. An attempt is made to simulate the realistic semi-diurnal cycle of turbulent dissipation in Liverpool Bay Region of Freshwater Inflow (ROFI) in the Irish Sea characterized by strong horizontal gradients and interactions with tidal flow. Turbulent dissipation cycles with a 25-h period using free-falling light yo-yo (FLY) dissipation profiler exhibits a strong asymmetry between ebb and flood. The above dynamics involving tidal straining during the ebb and mixing during the flood has been simulated using k–ε

An Improved Model Including Length Scale Anisotropy for the Pressure Strain Correlation of Turbulence

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Role of Parallel Computing in Numerical Weather Forecasting Models

and the alternative formulated turbulence scheme in a one-dimensional (1-D) dynamic model. The model is forced with observed tidal flow and horizontal gradients of temperature and salinity. Simulated dissipation cycles show good agreement with observation. The present work also involves a comparison of dissipation rate measurements in northern North Sea using the abovementioned turbulence schemes—the measurements being taken using free-falling shear probes and CTD (conductivity, temperature, and depth) sensors. The main forcing provided for the upper and bottom boundary layers are atmospheric forcing and tides, respectively. To compare the observations and model results, quantitative error measurements have also been studied which reveal the applicability of the alternative turbulence scheme.

CFD Analysis of The Hydraulic Turbine Draft Tube to Improve System Efficiency

The present paper explores the derivation of an alternative nonlinear eddy viscosity formulation based on Reynolds stress anisotropy and its implementation to numerical ocean models. This formulation takes into account the vorticity in addition to the mean strain rate. The proposed formulation does not include the stability function method which is a common approach in eddy viscosity calculations used in the present state-of-the-art numerical ocean models. Instead, it depends on the second invariant of anisotropy. Initially, the performance of the formulation is checked through a simple channel flow simulation. Consequently for model calibration, an idealised experiment of mixed-layer entrainment into stably stratified flow has been simulated and compared to empirical data. For sensitivity studies related to shear and stable stratification, concept of steady-state Richardson number is applied for homogeneous shear layer. Finally, the performance of the new formulation is tested by implementing it into one...